In Deki revision comments we had both, the comment the editor entered and the amount of changed words. I liked that and I think it's a useful information on the history page.
So instead of:
<my revision comment>
let's have:
<my revision comment>; xx words added, yy words removed
See for example:
https://developer.mozilla.org/en-US/docs/MathML/Element/math$history

And if an editors enters no revision comment at akk, there is currently no comment at all in the revision history. I would expect to have at least the amount of changed words then.
"xx words added, yy words removed"
(If no words were changed, Deki added "no changes" as a comment, but I hope Kuma will not save a new revision then anyway)

Contributor system64 has been working on this. This is pretty difficult to implement, for MDN or anywhere else.
Florian, David, Sheppy: What do you think about listing "(x% changed)" somewhere in the revision history instead? It would be easier to implement, but would it still provide you with the information you need?

(In reply to John Karahalis [:openjck] (PTO until April 29, 2013) from comment #2)
> Florian, David, Sheppy: What do you think about listing "(x% changed)"
> somewhere in the revision history instead? It would be easier to implement,
> but would it still provide you with the information you need?
It would be enormously more useful if it were something you would see while glancing through the list of changes in the revision dashboard (that's why we suggested adding it to the comment). The reason is simple: if you're flipping through the list in a hurry and see some enormous word change count on a long-standing article, that's a huge red-flag that someone has probably screwed something up.

(In reply to John Karahalis [:openjck] (PTO until April 29, 2013) from comment #4)
> We could add this information to the revision dashboard with either style.
> Would %-style be good enough in helping you find enormous changes?
Yeah, a percentage would be fine for that (although I'd still like to be able to see an actual number of words changed somewhere, but that could go in the history).